title: Prolongation of serum half-life of interleukin 2 and augmentation of lymphokine-activated killer cell activity by pepstatin in mice.
abstract: We reported previously using a murine model that the kidney is the organ involved in catabolism of exogenous human recombinant interleukin 2 (IL-2) and that cathepsin D, a major renal acid protease, is responsible for the degradation of IL-2. In the present report also using BALB/c mice we have investigated the effect of in vivo pepstatin, an acid protease inhibitor, treatment on serum half-life of IL-2, and generation of lymphokine-activated killer (LAK) cell activity. The in vivo pepstatin treatment by i.p. injection resulted in a significant reduction in the accumulation of 125I-IL-2 by the kidney in a reverse dose-response manner. Pepstatin treatment prolonged the serum half-life of 125I-IL-2, and the increase in serum half-life of 125I-IL-2 was pepstatin dose dependent. A significant reduction in renal cathepsin D activity, as monitored by the degradation of 125I-IL-2, was detected. In vivo pepstatin (0.6 mg/kg) treatment along with IL-2 (300,000 IU/mouse) daily for 3 or 6 days resulted in an augmentation of natural killer activity exhibited by freshly prepared and uncultured splenocytes against YAC-1 cells. An additional culturing of the splenocytes with IL-2 (3,000 IU/ml) in vitro for 1 day significantly enhanced the effect of in vivo pepstatin treatment; i.e., LAK cell activity generated from the splenocytes of animals treated with IL-2 plus pepstatin was greatly augmented in comparison with that treated with IL-2 alone. Phenotypic assessment by cell surface markers (Thy-1.2, Lyt-2, L3T4, and asialo-GM1) on the fresh splenocytes prepared from animals treated in vivo with pepstatin plus IL-2 revealed a decrease in the percentage of cells expressing Thy-1.2 and Lyt-2 and an increase in those carrying asialo-GM1. These results demonstrated that, as a result of in vivo pepstatin treatment, renal cathepsin D activity was greatly inhibited, which in turn reduced the degradation of circulating IL-2, then prolonged serum half-life of IL-2, and subsequently augmented natural killer and LAK cell activity. The in vivo pepstatin and IL-2 treatment decreased the T-cells and increased the natural killer-like LAK precursor cells, possibly also with an increase in its activity, which were further induced by in vitro IL-2 culture to generate an augmented LAK cell activity. This study also suggests the clinical potential of pepstatin in IL-2-related immunotherapy.
authors.affiliation: Department of Diagnostic Immunology Research and Biochemistry, Roswell Park Memorial Institute, Buffalo, New York 14263.
authors.forename: H
authors.initials: H
authors.lastname: Ohnishi
authors.forename: K M
authors.initials: KM
authors.lastname: Lin
authors.forename: T M
authors.initials: TM
authors.lastname: Chu
mesh_terms: D000818:Animals; D002402:Cathepsin D / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005260:Female; D006207:Half-Life; D007376:Interleukin-2 / Q000378:metabolism* / Q000493:pharmacokinetics; D007668:Kidney / Q000201:enzymology / Q000378:metabolism*; D015979:Killer Cells, Lymphokine-Activated / Q000187:drug effects*; D051379:Mice; D008807:Mice, Inbred BALB C; D009842:Oligopeptides / Q000494:pharmacology*; D010436:Pepstatins / Q000494:pharmacology*; D010641:Phenotype; D013154:Spleen / Q000166:cytology; D014018:Tissue Distribution
chemical_list: D007376:Interleukin-2; D009842:Oligopeptides; D010436:Pepstatins; D002402:Cathepsin D